1. Field of the invention
The present invention relates to a chemical mechanical polishing composition, and especially to a chemical mechanical composition suitable for metal polishing.
2. Description of the Prior Art
Following the tendency that critical dimensions of electronic elements get smaller and smaller and that layers of conductors required increase rapidly, electric resistance/capacitance time delay (RC Time Delay) will gravely influence the speed of operation of integrated circuits. In order to avoid time delay induced by reducing of the width of metallic wire and the problem on reliability of electron displacement, copper conductive material with low electric resistance and high ability of impedance against destruction of electron displacement is chosen in lieu of aluminum alloy. However, by the fact that the metallic copper has the character of being hard to be etched, another mode of damascening must be adopted for forming the metallic copper wire.
The so called damascening is that: a position for a copper wire is given by etching on a dielectric layer by the micro-patterning technique in the first place, then a copper film is formed by deposition on the dielectric layer to fill copper all over trenches on the dielectric layer, and at last, the copper film is removed by polishing using the technique of chemical mechanical polish (CMP), to leave copper in the trenches as metallic conductors. In the process of damascening, copper-chemical mechanical polish is a brand new technique, and has been the most important part in the metal damascening technique of copper conductors.
The chemical mechanical polishing mainly is to remove metal by polishing transversely; it works only when the mechanical and the chemical actions are used simultaneously; for metal being damascened in a dielectric layer, it has lower polish removal rate, so that copper wires embedded in the dielectric layer can be kept. However, in the technique of chemical mechanical polish for metal, the metal surface still often has the defects of metal dishing and erosion.
The phenomenon of metal dishing and erosion is highly in relation with the rate of polishing and uniformity, higher rate of polishing can increase yield per unit time, but it is subjected to accelerating the phenomenon of metal dishing and erosion; while inferior uniformity needs more polishing time to completely remove copper, thus more serious phenomenon of metal dishing and erosion is induced. Thereby, for eliminating the phenomenon of metal dishing and erosion, we must start from improvement of the rate of polishing and uniformity.
For the purpose of taking care of both the yield per unit time and preventing the phenomenon of metal dishing and erosion, normally the process of copper-chemical mechanical polish is divided into two steps. In the first stage, larger removal rate is used to remove bulk overburden copper to increase the yield per unit time. In the second stage, smaller removal rate is used to remove the remaining less copper, in order to avoid over erosion phenomenon on the copper in the trenches. Generally, the two stages of the copper polishing processes require changing the polishing composition, to meet the requirements of copper polishing for different stages. However, changing the polishing composition not only is not benefit to simplification of the processes, but also is probable to increase waste material.
U.S. Pat. No. 6,679,929 discloses a polishing composition which includes at least a kind of polishing abrasive with a aliphatic carboxylic acid having 10 carbon atoms, an alkali ingredient, an accelerating compound, an anticorrosive agent, hydrogen peroxide and water; although the polishing composition can lower the rate of etching of copper metal, removing rate of the bulk copper makes disadvantageous affect. A published document of U.S. patent no. 2004/0020135 discloses a polishing composition containing silicon dioxide, an oxidant, amino acid, triazole-based compound and copper metal polishing composition of water. The patent does not disclose using of a co-inhibitor that can slow down the rate of etching of the polishing composition on metal under the condition of maintaining a high polish removing rate; meantime that is applicable to the two stages of the copper polishing.
Therefore, it still needs to provide a chemical mechanical polishing composition with a high removing ability through polishing to effectively eliminate the phenomenon of metal dishing and erosion.